Potential always builds up between two electric conductors separated by an insulating body and capacitance refers to the capacity for potential buildup. By nature, capacitance increases as the conductors are brought closer to each other and decreases as they are taken farther away from each other.
A touch sensor takes advantage of this characteristic and detects the change in capacitance generated by a human finger, one conductor, approaching an electrode, the other conductor.
The relationship between capacitance in F (farad) and the distance between the electrodes can be represented by the formula below:

C=e×S/d

where e is the dielectric constant, S is the area of the electrode and d is the distance between the electrodes.

The capacitance generated by a metal object in or near the wiring or detection circuit. For higher sensitivity in a touch sensor, the smallest possible value is desirable. The value becomes larger if a ground line is near signal line wiring or the wiring area is large.

This is a value specific to a material showing its ability to retain potential. Generally, a relative dielectric constant, the ratio of the dielectric constant of the conductor to the dielectric constant of a vacuum, is used often. For use in an operating panel for a touch sensor, a higher relative dielectric constant allows greater detection distance and thicker material achieves higher dielectric constant.

ITO stands for indium tin oxide and is often used for transparent conductive film. The material was developed by Teijin about 20 years ago and has come to be manufactured and used worldwide. ITO, which allows passage of light and electricity, is used in functional components of many different products.